1. Field of the Invention
This invention relates generally to switching devices formed in silicon, and, more particularly, to a light activated, silicon controlled switch.
2. Description of the Related Art
A thyristor is a semiconductor switch whose bistable action depends on p-n-p-n structure regenerative feedback. Thyristors can take many forms but in general they are solid-state switches that act is open circuits capable of withstanding a rated voltage until they are triggered. When the thyristor is triggered it becomes a low impedance current path and remains in that condition until the current stops or drops below the minimum value called a holding level. Once the thyristor has been triggered, the trigger current can be removed without turning off the device. Silicon controlled rectifiers and triacs are both members of the thyristor family. Structurally, thyristors consist of alternating layers of opposite p-type and n-type silicon. For example, the simplest thyristor design includes four layers including two p-type layers that alternate with two n-type silicon layers.
Thyristors are typically triggered by applying a current to one or more elements in the thyristor. For example, a control circuit may be used to supply a trigger current to the thyristor when some condition enforced by the control circuit is satisfied. The critical current required to trigger the thyristor is typically called the latching current. In some cases, the control circuit provides the trigger current in response to an optical signal generated by an optical source. The optical source is typically an external source that is constructed of a compound semiconductor, while the receiver is silicon.
The present invention is directed to addressing the effects of one or more of the problems set forth above.